Britons around the world have been warned they face a heightened risk of terrorist attacks during military action against Iraq.

The Foreign Office last night issued urgent new travel advice for travellers and tourists to stay vigilant hours before the blitz on Saddam began.

It stated: "The risk of indiscriminate terrorist attacks in public places, including tourist sites, will be especially high during military action in Iraq.

"You should be vigilant, take sensible precautions, be aware of local sensibilities, monitor the media and check our travel advice for the country you live in or plan to visit."

The Foreign Office also issued new advice relating to neighbouring Jordan, advising against all travel to the kingdom.

The advice stated: "Military action in Iraq is imminent.

"There is an increased threat from terrorism to the safety of British nationals in neighbouring countries.

"There is also a risk of the use of chemical and biological weapons by Iraq in the event of hostilities.

" Jordan might be affected. We advise against travel to Jordan.

" If you are already in Jordan, we advise you to consider leaving while air routes remain open, unless your presence is essential.

"If Jordanian airspace is closed, or flights are disrupted, we advise British nationals to adopt a low profile, minimise travel and practice sensible security precautions."

Britons living in Kuwait, Israel and the Occupied Territories, Jordan, Bahrain, Syria, Qatar, Oman and Saudi Arabia were warned in the event of a chemical or biological attack, they should follow the local authorities' and emergency services' instructions.

The Foreign Office has already advised all British citizens to leave Iraq immediately and hinted Western reporters could be lured close to military targets to be used by the military as human shields.

It also warned of a potential breakdown in law and order in Iraq following military strikes.